editing feed.php

Sorry for the slow response, I’ve been away.

The parameter can resolve to any integer representing your desired time in seconds. For 30 minutes, the parameter could be 30*60 or 1800.

However, you must never directly alter core files this way. You should learn how to use the filters provided, such as the one in your example: ‘wp_feed_cache_transient_lifetime’.

There’s several places you can place code to hook filters, the functions.php file of your theme, or preferably a child theme, or a simple plugin. It’s good practice to create a site specific plugin to contain all such little hacks as this.

Your hook code in this case would look like this:

add_filter('wp_feed_cache_transient_lifetime', 'sb_feed_time', 10, 2 );
function sb_feed_time( $time, $url ){
   return 1800;
}

This example collects the passed parameters, but ignores them. The parameters could be used to, for example, extend the cache time by 30% for particular URLs only.

😀 Withholding trade “secrets” in an open source community is… is… aw nuts, is so ridiculous I can’t even properly articulate my thoughts!

In this particular case, there is absolutely no difference between altering the core file with a new number or doing so via a filter. In other cases, it depends on how you alter the core code and if a filter or action is available.

There is no problem altering core files on a temporary basis as part of your development process, but it is improper as a permanent solution. If you do share such alterations in a public forum such as this, it’s a good idea to clarify your intent so no one is led to believe altering core files is a proper solution.

You are free to do what you like on your own site of course, but altering core files in some cases can lead to frustration if there turns out to be no filter or action to hook to do as you need. Better to use filters as needed from the start to ensure the chosen approach is viable. You can avoid multiple edits in various themes by adding filters from a single common plugin that is applied regardless of which theme you happen to be testing. Filters work equally well when added from a plugin instead of a theme.